1. Field of the Invention
The present invention relates to an adhesively bonded structure between a dynamic power detecting element and an object to be detected, and more particularly, to an improvement of an adhesively bonded structure in which a dynamic power detecting element formed of a ferromagnetic material is adhesive bonded to an object to be detected through an adhesive bond.
2. DESCRIPTION OF THE PRIOR ART
The dynamic power detecting element has been conventionally adhesively bonded to an object to be detected through an adhesive bond formed of an adhesive alone (for example, see Japanese Patent Application Laid-open No. 182630/62).
Some ferromagnetic materials have a positive magnetostriction, e,g., amorphous alloys produce a phenomenon that when a tensile is applied thereto the magnetic resilience in a direction of such tension is reduced to facilitate the magnetization in such direction, i.e., a so-called stress-magnetization effect. When the torque of a rotating shaft, which is an object to be detected, is detected by utilizing this stress-magnetization effect, a strain produced in the rotating shaft is introduced to a torque detecting element serving as a dynamic power detecting element made from a thin amorphous alloy strip to detect the torque. Therefore, it is desirable that the adhesive bond is thin and uniform in thickness over the entire length thereof.
However, if an adhesive bond is formed from an adhesive alone as described above, the adhesive bond is difficult to be formed into a decreased and uniform thickness, resulting in problems of a dispersion of torque detected values, a reduction in detecting sensitivity of the torque detecting element and so on.
In addition, the torque detecting element is required to exhibit a rectilinear torque-output characteristic irrespective of temperature conditions, but there is also the following problem: The above-described adhesive is commonly formed from a synthetic resin and hence, has a large linear thermal expansion coefficient peculiar to the resin. Consequently, the torque detecting element is subjected to influences of shrinkage and expansion of the adhesive bond in increased and decreased temperatures to lose the linearity of the torque-output characteristic.